1. Field of the Invention
The present invention relates to the manufacture of books and particularly to the rounding of the backs of book blocks as part of a bookbinding operation. More specifically, this invention is directed to book block back-rounding apparatus capable of high speed operation and especially to such apparatus wherein rounding rollers which act on the book block travel in synchronism with and cooperate with continuously movable book block clamps of a transport system which moves the blocks into and out of the back-rounding station. Accordingly, the general objects of the present invention are to provide novel and improved methods and apparatus of such character.
2. Description of the Prior Art
In the manufacture of books, and particularly in the binding of hard cover books, it is customary to perform a rounding operation on the book block. As a result of this rounding operation, the desired rounded shape is imparted to the block back and the trimmed block front. In the majority of book block processing machines presently employed, the rounding operation results from implementation of the well-known roller-rounding principle. During a roller-rounding operation, the individual leaves or printed sheets of a book block are smoothly and progressively displaced relative to each other as a result of the simultaneous engagement of the opposite sides of the book block by rotatably driven, grooved rounding rollers. The rotational force is applied to the book block sides concurrently with the application of pressure and is caused to occur through a defined rotation angle. Accordingly, as the book block passes through the rounding rollers, the leaves or printed sheets are pushed progressively further forwards as an inverse function of distance from the book block center.
For an example of prior art apparatus for rounding and simultaneously shaping book block backs, reference may be had to German Patent 1,536,507. This German patent discloses a bookbinding machine including a transport system which, in stepwise fashion, conveys book blocks longitudinally through a series of processing stations. The transport system comprises pairs of cooperating clamping jaws, the jaws of each pair facing one another across a variable gap. The cooperating clamping jaws engage the sides of a book block in order to convey it into the shaping station where it is engaged by the rounding rollers. In the shaping station, the book block enters the operating area of a pair of grooved rounding rollers which, once the clamping jaws have been retracted from the book block sides, act on the block to cause the shaping thereof in the manner briefly discussed above.
In order to permit operation of prior art book block rounding apparatus in an efficient manner, and particularly with an acceptably high through-put, various mechanical expedients have been attempted. Thus, for example, attempts have been made to increase efficiency by employing light-weight materials for a substantial percentage of the moving parts of the transport system to thereby increase operational speed and thus increase the linear speed at which the book blocks are conveyed from station-to-station. Nevertheless, considering the start-stop mode of operation of prior art apparatus such as that disclosed in the above-referenced German patent, prior art book block rounding apparatus can be utilized only within a limited range of outputs.